2,2,3,3-tetrafluorooxethane is a useful raw material compound for producing fluorine-containing rubber polymers, etc. For example, 2,2,3,3-tetrafluorooxethane can readily undergo polymerization reaction in the presence of an alkali metal halide, and fluorination of the hydrogen atoms of the resulting polyfluoropolyether polymer F(CH2CF2CF2O)nCH2CF2COF by a fluorine gas can give fluorine oil such as perfluoropolyether polymers F(CF2CF2CF2O)nCF2CF2COF or F(CF2CF2CF2O)nCF2CF3. React-ion with an alkali metal halide can give a 2,2-difluoropropionic acid derivative represented by the following general formula as raw materials for producing fluorine-containing rubber polymers:XCH2CF2COF(X: Cl, Br or I)
It is known that 2,2,3,3-tetrafluorooxethane having such effective uses can be produced by reaction of tetrafluoroethylene with a compound of formaldehyde generation source in anhydrous hydrogen fluoride.                Patent Literature 1: JP-B-2-37904        
It is also reported that 2,2,3,3-tetrafluorooxethane can be obtained as a by-product in the production of 2,2,3,3,3-pentafluoropropanol CF3CF2CH2OH by reaction of tetrafluoroethylene with formaldehyde in anhydrous hydrogen fluoride, but only in a small amount because it is a by-product, and thus cannot be used as raw materials in the industrial scale.                Non-Patent Literature 1: J. Org. Chem. 28, 492-4(1963)        